Vacuum pump system and vacuum pump RPM control method

ABSTRACT

Disclosed is a vacuum pump system which, even when a plurality of vacuum pumps are arranged, is capable of preventing a beat and low-frequency vibration by matching the RPM and phases of the rotary members of the vacuum pumps with each other. Control is performed such that the rotating conditions of the rotary members detected by a slave detecting device are in synchronism with the rotating condition of the rotary member detected by a master detecting device. Alternatively, control is performed such that the rotating conditions of the rotary members detected by a detecting device are in synchronism with a synchronous signal output from a synchronous signal generating device.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a vacuum pump system and avacuum pump RPM control method, and more particularly, to a vacuum pumpsystem and a vacuum pump RPM control method in which even when aplurality of vacuum pumps are arranged, the RPM and phases of the vacuumpumps are matched with each other, thereby preventing a beat andlow-frequency vibration.

[0003] 2. Description of the Related Art

[0004] As a result of the recent development of electronics, there is arapid increase in the demand for semiconductor devices such as memoriesand integrated circuits.

[0005] Semiconductor devices are manufactured, for example, by dopinghighly pure semiconductor substrates with impurities to impartelectrical properties thereto, or forming minute circuits onsemiconductor substrates by etching.

[0006] To avoid the influence of dust or the like in the air, suchoperations have to be performed in a high vacuum chamber. To evacuatethe chamber, a vacuum pump is generally used. In particular, aturbo-molecular pump, which is a kind of vacuum pump, is widely usedsince it involves little residual gas and is easy to maintain.

[0007] A semiconductor manufacturing process includes a number of stepsin which various process gases are caused to act on semiconductorsubstrates, and the turbo-molecular pump is used not only to create avacuum in a chamber, but also to discharge these process gases from thechamber.

[0008] Further, a vacuum pump is also used in equipment such as anelectron microscope to create a high vacuum state in the chamberaccommodating the electron microscope or the like to thereby preventrefraction of the electron beam or the like due to the presence of dustor the like.

[0009] In this way, vacuum pumps are widely used in various fields.Nowadays, there are many occasions where vacuum pumps are used.Regarding the production of semiconductors, there is a plan forproducing a semiconductor wafer larger than the conventional ones.Regarding the field of electron microscope or the like, an electronmicroscope or the like larger than the conventional ones is beingrealized as an apparatus, with the installation of additional equipmentbeing planned.

[0010] For such purposes, a plurality of vacuum pumps may be used. FIG.8 schematically shows such a pump system configuration.

[0011] In FIG. 8, connected to the chamber 300 of an apparatusconstituting the object of suction which is to be subjected to pressurereduction through suction, are a plurality of vacuum pumps, for example,turbo-molecular pumps 100A, 100B, 100C, and 100D.

[0012] Actually, there exist valves, such as opening/closing valves, anddampers for absorbing vibration between the turbo-molecular pumps 100A,100B, 100C, and 100D and the chamber 300 constituting the object ofsuction which is to be subjected to pressure reduction through suctionby the turbo-molecular pumps. However, such components are omitted inthe drawing for the sake of simplification.

[0013] Further, the turbo-molecular pumps 100A, 100B, 100C, and 100D arerespectively controlled by control devices 200A, 200B, 200C, and 200D.FIG. 9 is a longitudinal sectional view of one of these turbo-molecularpumps.

[0014] In FIG. 9, the turbo-molecular pump 100 has an inlet port 101 atthe upper end of an outer cylinder 127. Inside the outer cylinder 127,there is provided a rotary member 103 having in its periphery aplurality of rotary blades 102 a, 102 b, 102 c, . . . formed radially ina number of stages and constituting turbine blades for sucking anddischarging gas.

[0015] At the center of this rotary member 103, there is mounted a rotorshaft 113, which is supported so as to levitate and controlled inposition by, for example, a so-called 5-axis control magnetic bearing.

[0016] In an upper radial electromagnet 104, four electromagnets arearranged in pairs in the X- and Y-axis. An upper radial sensor 107composed of four electromagnets is provided in close vicinity to and incorrespondence with the upper radial electromagnet 104. The upper radialsensor 107 detects radial displacement of the rotor shaft 113 and sendsthe detection result to the control device 200.

[0017] Based on the displacement signal from the upper radial sensor107, the control device 200 controls the excitation of the upper radialelectromagnet 104 through a compensation circuit (not shown) having aPID adjusting function, thereby adjusting the upper radial position ofthe rotor shaft 113.

[0018] The rotor shaft 113 is formed of a material having high magneticpermeability (e.g., iron), and is attracted by the magnetic force of theupper radial electromagnet 104. Such adjustment is conductedindependently in the X- and Y-axis directions.

[0019] Further, a lower radial electromagnet 105 and a lower radialsensor 108 are arranged in the same manner as the upper radialelectromagnet 104 and the upper radial sensor 107, adjusting the lowerradial position of the rotor shaft 113 in the same manner as the upperradial position thereof.

[0020] Further, axial electromagnets 106A and 106B are arranged with ametal disc 111 having a circular plate-like shape and which is providedat the bottom of the rotor shaft 113 being therebetween. The metal disc111 is formed of a material having high magnetic permeability like iron.To detect axial displacement of the rotor shaft 113, there is providedan axial sensor 109 whose axial displacement signal is sent to thecontrol device 200.

[0021] And, based on this axial displacement signal, the axialelectromagnets 106A and 106B are excitation-controlled through acompensation circuit (not shown) with a PID adjusting function of thecontrol device 200. The axial electromagnet 106A upwardly attracts themetal disc 111 by magnetic force, and the axial electromagnet 106Bdownwardly attracts the metal disc 111.

[0022] In this way, the control device 200 appropriately adjusts themagnetic force exerted on the metal disc 111 by the axial electromagnets106A and 106B to cause the rotor shaft 113 to magnetically levitate inthe axial direction, supporting it in a space in a non-contact state.

[0023] A motor 121 is a so-called three-phase brushless motor. FIG. 10is a circuit diagram showing this motor and a motor control circuit.

[0024] In FIG. 10, a double-pole (N-pole and S-pole) permanent magnetconstituting the rotor side component of the motor 121 is mounted to theperiphery of the rotor shaft 113.

[0025] And, the motor 121 has as the stator side components threerotation detecting sensors 124A, 124B, and 124C, and these rotationdetecting sensors 124A, 124B, and 124C are arranged so as to surroundthe rotor shaft 113. Further, the rotation detecting sensors 124A, 124B,and 124C are arranged at an interval of approximately 120 degrees.

[0026] The rotation detecting sensors 124A, 124B, and 124C are, forexample, semiconductor hall sensors, and adapted to detect the magneticflux density of the permanent magnet on the rotor side of the motor 121,thereby detecting the RPM, phase, etc. of the rotor shaft 113.

[0027] Further, the motor 121 has on the stator side thereof three-phasemotor windings 126U, 126V, and 126W. These motor windings 126U, 126V,and 126W are also arranged so as to surround the rotor shaft 113 (in thedrawing, they are shown separately from the rotor side of the motor 121for the sake of convenience).

[0028] And, the motor windings 126U, 126V, and 126W are connected to amotor driving circuit 222 arranged in the control device 200.

[0029] This motor driving circuit 222 is equipped with a DC power source238, and six transistors 226, 228, 230, 232, 234, and 236 forming athree-phase bridge. A predetermined gate signal is input to the baseterminal of each of the transistors 226, 228, 230, 232, 234, and 236. Bythis gate signal, the AC voltage supplied to the motor windings 126U,126V, and 126W is pulse-width-controlled (PWM control).

[0030] The detection signal detected by the rotation detecting sensor124A is input to an RPM detecting circuit 240 arranged in the controldevice 200, and the detection signals detected by the rotation detectingsensors 124A, 124B, and 124C are input to a gate signal generatingcircuit 246.

[0031] The RPM detecting circuit 240 detects the RPM of the rotor shaft113 based on the detection signal detected by the rotation detectingsensor 124A, and outputs this detected RPM to a comparator 242.

[0032] Input to the comparator 242 is a predetermined reference RPMpre-set by a reference value setting circuit 244. And, the comparator242 compares this predetermined reference RPM with the RPM of the rotorshaft 113 detected by the RPM detecting circuit 240, and outputs thecomparison result to the gate signal generating circuit 246. Thereference value setting circuit 244 is formed, for example, by a crystaloscillator.

[0033] When the comparison result of the comparator 242 indicates thatthe RPM of the rotor shaft 113 is not less than the reference RPM, thegate signal generating circuit 246 compares it with the detectionsignals from the rotation detecting sensors 124A, 124B, and 124C, andcontrols the gate signals of the transistors 226, 228, 230, 232, 234,and 236 so as to cause the rotor shaft 113 to rotate at low speed. Whenthe RPM of the rotor shaft 113 is less than the reference RPM, the gatesignals are controlled so as to cause the rotor shaft 113 to rotate athigh speed.

[0034] In this way, the motor 121 is controlled to perform rotationcontrol on the rotor shaft 113.

[0035] A plurality of stationary blades 123 a, 123 b, 123 c, . . . arearranged so as to be spaced apart from the rotary blades 102 a, 102 b,102 c, . . . of the rotor shaft 113 by small gaps. The rotary blades 102a, 102 b, 102 c, . . . are inclined by a predetermined angle from aplane perpendicular to the axis of the rotor 113 in order to convey themolecules of exhaust gas downwards through collision.

[0036] The stationary blades 123 are also inclined by a predeterminedangle from a plane perpendicular to the axis of the rotor shaft 113, andarranged alternately with the rotary blades 102 so as to extend towardthe inner side of the outer cylinder 127.

[0037] And, at one end, the stationary blades 123 are supported in astate in which they are fitted into the spaces between a plurality ofstationary blade spacers 125 a, 125 b, 125 c, . . . stacked together.

[0038] The stationary blade spacers 125 are ring-like members which areformed, for example, of aluminum, iron, stainless steel, copper, or analloy containing some of these metals as a component.

[0039] The outer cylinder 127 is fixed to the outer periphery of thestationary blade spacers 125 with a small gap therebetween. A baseportion 129 is arranged at the bottom of the outer cylinder 127, and athreaded spacer 131 is arranged between the lower portion of thestationary blade spacers 125 and the base portion 129. And, an exhaustport 133 is formed below the threaded spacer 131 of the base portion129, and communicates with the exterior.

[0040] The threaded spacer 131 is a cylindrical member formed ofaluminum, copper, stainless steel, iron, or an alloy containing some ofthese metals as a component, and has in its inner peripheral surface aplurality of streaks of spiral thread grooves 131 a.

[0041] The direction of the spiral of the thread grooves 131 a isdetermined such that when the molecules of the exhaust gas move in therotating direction of the rotary member 103, these molecules areconveyed toward the exhaust port 133.

[0042] At the lowermost portion of the row of rotary blades 102 a, 102b, 102 c, . . . of the rotary member 103, a rotary blade 102 d extendsvertically downwards. The outer peripheral surface of this rotary blade102 d is cylindrical, and juts out toward the inner peripheral surfaceof the threaded spacer 131 so as to be in close vicinity to the innerperipheral surface of the threaded spacer 131 with a predetermined gaptherebetween.

[0043] The base portion 129 is a disc-like member forming the baseportion of the turbo-molecular pump 100, and is generally formed of ametal, such as iron, aluminum, or stainless steel. Further, the baseportion 129 physically retains the turbo-molecular pump 100 and, at thesame time, serves as a heat conduction path. Thus, it is desirable forthe base portion 129 to be formed of a metal which has rigidity and highheat conductivity, such as iron, aluminum, or copper.

[0044] In this construction, when the rotor shaft 113 is driven by themotor 121 to rotate with the rotary blades 102, exhaust gas from thechamber is sucked in through the inlet port 101 by the action of therotary blades 102 and the stationary blades 123.

[0045] The exhaust gas sucked in through the inlet port 101 flowsbetween the rotary blades 102 and the stationary blades 123 to beconveyed to the base portion 129. At this time, the temperature of therotary blades 102 is increased due to the frictional heat generated whenthe exhaust gas comes into contact with the rotary blades 102, the heatconduction generated in the motor 121, etc., and this heat istransmitted to the stationary blades 123 side by radiation or theconduction due to the gas molecules of the exhaust gas, etc.

[0046] The stationary blade spacers 125 are connected together in theouter periphery, and transmit to the exterior the heat received by thestationary blades 123 from the rotary blades 102, the frictional heatgenerated when the exhaust gas comes into contact with the stationaryblades 123, etc.

[0047] The exhaust gas conveyed to the base portion 129 is sent to theexhaust port 133 while being guided by the thread grooves 131 a of thethreaded spacer 131.

[0048] In the above-described example, the threaded spacer 131 isarranged in the outer periphery of the rotary blade 102 d, and thethreaded grooves 131 a are formed in the inner peripheral surface of thethreaded spacer 131. However, in some cases, the threaded grooves may beformed in the outer peripheral surface of the rotary blade 102 d, with aspacer with a cylindrical inner peripheral surface being arranged aroundthe same.

[0049] Further, in order to prevent the gas sucked in through the inletport 101 from entering the electrical component section formed by themotor 121, the lower radial electromagnet 105, the lower radial sensor108, the upper radial electromagnet 104, the upper radial sensor 107,etc., the electrical component section is covered with a stator column122, and the interior of this electrical component section is maintainedat a predetermined pressure by a purge gas.

[0050] Thus, piping (not shown) is arranged in the base portion 129, andthe purge gas is introduced through this piping. The introduced purgegas flows through the gap between the protective bearing 120 and therotor shaft 113, the gap between the rotor and stators of the motor 121,and the gap between the stator column 122 and the rotary blades 102before it is sent to the exhaust port 133.

[0051] Note that the turbo-molecular pump 100 has to be controlled basedon individually adjusted specific parameters (e.g., the specific modeland the characteristics corresponding to the model). To store thesecontrol parameters, the main body of the turbo-molecular pump 100contains an electronic circuit portion 141.

[0052] The electronic circuit portion 141 is composed of electronicparts, such as a semiconductor memory like EEP-ROM, and a semiconductordevice for the access thereto, a board 143 for mounting the electronicparts, etc.

[0053] This electronic circuit portion 141 is accommodated in the lowercentral portion of the base portion 129 constituting the lower portionof the turbo-molecular pump 100, and is closed by a hermetic bottomcover 145.

[0054] In some cases, the process gas is introduced into the chamber athigh temperature for enhanced reactivity. And, when cooled to a certaintemperature at the time of discharge, such process gas may be turnedinto solid to precipitate a product in the exhaust system.

[0055] And, such process gas attains low temperature inside theturbo-molecular pump 100 to be turned into solid, adhering to the innersurfaces of the turbo-molecular pump 100 to be deposited thereon.

[0056] Suppose, for example, SiCl₄ is used as the process gas in an Aletching apparatus. As can be seen from vapor pressure curve, under alow-vacuum state (760[torr] to 10⁻²[torr]) and at low temperature(approximately 20[C.]), a solid product (e.g., AlCl₃) is precipitated,adhering to the inner surfaces of the turbo-molecular pump 100 to bedeposited thereon.

[0057] When a precipitate of the process gas is deposited on the innersurfaces of the turbo-molecular pump 100, the deposited substance willnarrow the pump flow passage, resulting in a deterioration in theperformance of the turbo-molecular pump 100.

[0058] The above-mentioned product is likely to solidify and adhere inlow-temperature portions, such as the portion near the exhaust port,and, in particular, near the rotary blades 102 and the threaded spacer131. Conventionally, this problem is solved by winding a heater (notshown) and an annular water cooling tube 149 around the outer peripheryof the base portion 129, etc. and embedding a temperature sensor (notshown) (e.g., a thermistor) in, for example, the base portion 129 toperform heating by the heater and cooling by the water cooling tube 149(hereinafter referred to as TMS (temperature management system) so as tomaintain the base portion 129 at a fixed high temperature (settemperature).

[0059] When, as shown in FIG. 8, a plurality of turbo-molecular pumps100A, 100B, 100C, and 100D are used as the vacuum pumps, the controldevices 200A, 200B, 200C, and 200D are conventionally subjected toindependent control.

[0060] In this case, the control devices 200A, 200B, 200C, and 200D arecapable of accurately setting the RPM of the rotary members 103 of therespective turbo-molecular pumps 100A, 100B, 100C, and 100D with anerror of within several Hz with respect to the rated RPM of, forexample, 48,000 (800 Hz).

[0061] However, even when the rated RPM of the rotary members 103 of theturbo-molecular pumps 100A, 100B, 100C, and 100D are set to the samevalue, a minute difference in RPM can be generated between the rotarymembers 103 of the turbo-molecular pumps 100A, 100B, 100C, and 100D withan error of within several Hz as described above. For example, therotary member of the turbo-molecular pump 100A may rotate at 48,000 rpm(800 Hz) while that of the turbo-molecular pump 100B is rotating at48,060 rpm (801 Hz).

[0062] In such cases, the difference in RPM between the rotary members103 generates a beat in the turbo-molecular pumps 100A, 100B, 100C, and100D, which can generate low-frequency vibration attributable to thebeat.

[0063] Such low-frequency vibration varies depending upon thecombination of the model, volumes, etc. of the turbo-molecular pumps 100arranged, and is difficult to eliminate even with the above-mentioneddampers provided between the turbo-molecular pumps 100A, 100B, 100C, and100D and the chamber 300. If this vibration is transmitted from theturbo-molecular pumps 100A, 100B, 100C, and 100D to the chamber 300side, there is the danger of the measurement with the electronicmicroscope or the like or the production of semiconductor devices in thechamber 300 being adversely affected.

SUMMARY OF THE INVENTION

[0064] The present invention has been made in view of theabove-mentioned problem in the prior art. It is an object of the presentinvention to provide a vacuum pump system and a vacuum pump RPM controlmethod in which even when a plurality of vacuum pumps are arranged, theRPM and phases of the rotary members of the vacuum pumps are matchedwith each other, thereby preventing a beat and low-frequency vibration.

[0065] According to the present invention, there is provided a vacuumpump system equipped with N vacuum pumps each of which is equipped witha rotary member and a motor for rotating the rotary member and which aremounted side by side to equipment from which a predetermined gas is tobe sucked, and control devices connected to the vacuum pumps and adaptedto control at least one of RPM and rotation phases representing rotatingconditions of the rotary members, the vacuum pump system comprising:setting means for setting one of the control devices as a master controldevice and (N−1) control devices excluding the master control device asslave control devices; master detection means for detecting the rotatingcondition of the rotary member of a master vacuum pump of the vacuumpumps to which the master control device is connected; slave detectionmeans for detecting the rotating conditions of the rotary members ofslave vacuum pumps of the vacuum pumps to which the slave controldevices are connected; and control means for controlling such that therotating conditions of the rotary members detected by the slavedetection means are in synchronism with the rotating condition of therotary member detected by the master detection means.

[0066] The master control device outputs data on the rotating conditionof the rotary member of the master vacuum pump. The slave controldevices, on the other hand, take in the data on the rotating conditionof the rotary member of the master vacuum pump. And, the control meansperforms control such that the rotating conditions of the rotary membersof the slave vacuum pumps are in synchronism with the rotating conditionof the rotary member of the master vacuum pump.

[0067] Due to this arrangement, even when a plurality of vacuum pumpsare arranged, the RPM and phases of the rotary members of the vacuumpumps are matched with each other, thereby making it possible to preventa beat and low-frequency vibration.

[0068] When the master vacuum pump is stopped, the rotating conditionsof the rotary members of the slave vacuum pumps may be controlledthrough comparison with reference RPM and rotation phase.

[0069] Due to this arrangement, even when a plurality of vacuum pumpsare arranged, the RPM and rotation phases of the rotary members of thevacuum pumps are matched with each other, thereby making it possible toprevent a beat and low-frequency vibration. Thus, even when the mastercontrol device is stopped, it is possible to continue operation withoutstopping the slave control devices.

[0070] Further, when the master vacuum pump is stopped, it is alsopossible to switch one of the slave devices to a new master controldevice and to re-start the operation using it as the master controldevice.

[0071] Due to this arrangement, even when the maser control device isstopped, it is possible to continue synchronous operation with theremaining slave control devices alone, without stopping the slavecontrol devices.

[0072] Further, in this case, it is possible to set a predeterminedorder for the switching of the remaining slave control devices to themaster device. And, the predetermined order may be set based, forexample, on the uptime of the vacuum pumps, the volume of the vacuumpumps, failure history, etc., or they may be set manually by theoperator, etc.

[0073] Further, in a case in which only one slave vacuum pump is inoperation, with the other vacuum pumps being at rest, the rotatingcondition of the rotary member of that slave vacuum pump may be comparedwith a reference RPM and rotation phase, rotation control on the rotarymember being performed based on the comparison result.

[0074] This arrangement makes it possible to continue operation evenwith only one vacuum pump.

[0075] Further, it is also possible to detect failures in the controldevices and vacuum pumps.

[0076] This makes it possible to stop any vacuum pump out of order.

[0077] Further according to the present invention, a vacuum pump systemequipped with N vacuum pumps each of which is equipped with a rotarymember and a motor for rotating the rotary member and which are mountedside by side to equipment from which a predetermined gas is to besucked, and control devices connected to the vacuum pumps and adapted tocontrol at least one of RPM and rotation phases representing rotatingconditions of the rotary members, the vacuum pump system comprising:synchronous signal generating means for generating and outputting apredetermined synchronous signal; detecting means for detecting therotating conditions of the rotary members of the vacuum pumps; andcontrol means for controlling such that the rotating conditions of therotary members detected by the detecting means are in synchronism withthe synchronous signal output from the synchronous signal generatingmeans.

[0078] Based on the predetermined synchronous signal generated by thesynchronous signal generating means, the RPM and phases of the motorsare adjusted simultaneously, with the result that the RPM and phases ofthe motors are matched with each other.

[0079] And, since the synchronous signal is generated based on a crystaloscillator or the like, it is possible to further enhance the controlaccuracy. Thus, no beat or low-frequency vibration is generated. Thus,even when a plurality of vacuum pumps are arranged, it is possible toprevent a beat and low-frequency vibration by matching the RPM andphases of the rotary members of the vacuum pumps.

[0080] Further according to the present invention, a vacuum pump systemincludes: a rotary member; a motor for rotating the rotary member;detecting means for detecting at least one of RPM and rotation phaserepresenting rotating condition of the rotary member; internalcomparison means for comparing the rotating condition of the rotarymember detected by the detecting means with at least one of a referenceRPM and rotation phase; external comparison means for comparing therotating condition of the rotary member detected by the detecting meanswith an external synchronous signal; switching means for selecting thetransmission of the synchronous signal to the exterior or the receptionof the synchronous signal from the exterior based on a predeterminedswitching signal, and which is input with the comparison result of theinternal comparison means and the comparison result of the externalcomparison means and outputs an output signal which is selected from oneof the input comparison results based on the switching signal; androtation control means for controlling the rotating condition of therotary member based on the output signal output from the switchingmeans.

[0081] The switching means effects selection between transmission andreception of the synchronous signal based on the predetermined switchingsignal. Further, based on the predetermined switching signal, theswitching means effects selection as to whether the rotating conditionof the rotary member is to be controlled with respect to a reference RPMand rotation phase or with respect to an external synchronous signal.

[0082] This facilitates switching of the operation.

[0083] The vacuum pump device composed of a rotary member, a motor, adetecting means, an internal comparison means, an external comparisonmeans, a switching means, and a rotation control means may be set as themaster device or a slave device by the switching signal.

[0084] And, it is also possible to perform control such that therotating condition of the rotary member is output to the exterior fromthe master device as a synchronous signal, and that the rotatingcondition of the rotary member of the master device is controlled basedon the result of comparison with reference RPM and rotation phase. Theslave devices may receive a synchronous signal output from the masterdevice, the rotating conditions of the rotary members of the slavedevices being controlled based on the result of comparison with thissynchronous signal.

[0085] This makes it possible to perform control such that the rotatingconditions of the rotary members of the slave devices are in synchronismwith the rotating condition of the rotary member of the master device.

[0086] Further, the communication using the synchronous signal may beconducted through a wired or wireless system.

[0087] This makes it possible to select a method allowing easycommunication taking into account the condition of the place where thevacuum pump devices, etc. are arranged.

[0088] Further, the present invention relates to a vacuum pump RPMcontrol method for a vacuum pump system equipped with N vacuum pumpseach of which is equipped with a rotary member and a motor for rotatingthe rotary member and which are mounted side by side to equipment fromwhich a predetermined gas is to be sucked, and control devices connectedto the vacuum pumps and adapted to control the RPM of the rotarymembers, the method being characterized in that the RPM of the rotarymembers are all controlled to be the same.

[0089] Due to this arrangement, there is no need for both the RPM andphases of the rotary members to be always matched with each other. Whensolely the RPM of the rotary members of all the vacuum pumps are matchedwith each other, it is possible to prevent a beat and, further,low-frequency vibration.

BRIEF DESCRIPTION OF THE DRAWINGS

[0090] In the accompanying drawings:

[0091]FIG. 1 is a schematic structural diagram showing a pump systemaccording to a first embodiment of the present invention;

[0092]FIG. 2 is a circuit diagram showing a motor and a motor controlcircuit according to the first embodiment of the present invention;

[0093]FIG. 3 is a diagram showing how switching is effected by amaster/slave signal;

[0094]FIG. 4 is a diagram showing a phase matching process in a slavedevice;

[0095]FIG. 5 is a schematic structural diagram showing a pump systemaccording to a second embodiment of the present invention;

[0096]FIG. 6 is a diagram showing how switching between slave and masteris effected in a control device;

[0097]FIG. 7 is a schematic structural diagram showing a pump systemaccording to a fourth embodiment of the present invention;

[0098]FIG. 8 is a schematic structural diagram showing a conventionalpump system;

[0099]FIG. 9 is a longitudinal sectional view of a turbo-molecular pump;and

[0100]FIG. 10 is a circuit diagram showing a conventional motor andmotor control circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0101] A first embodiment of the present invention will now bedescribed.

[0102]FIG. 1 is a schematic structural diagram showing a pump systemaccording to the first embodiment of the present invention, and FIG. 2is a circuit diagram showing a motor and a motor control circuit. Thecomponents which are the same as those of FIGS. 8 to 10 are indicatedwith the same reference numerals, and a description of such componentswill be omitted.

[0103] In FIG. 1, the pump system of this embodiment is equipped with asynchronous operation controller 500. This synchronous operationcontroller 500 is capable of communicating with each of the controldevices 400A, 400B, 400C, and 400D.

[0104] Specifically, the synchronous operation controller 500 outputsthe master/slave signal 502 to each of the control devices 400A, 400B,400C, and 400D. As stated below, this master/slave signal 502 determineswhich of the control devices 400A, 400B, 400C, and 400D is to serve asthe master device and which of them is to serve as the slave device.

[0105] Communication is effected between the control devices 400A, 400B,400C, and 400D by a rotation synchronization signal 501.

[0106] In FIG. 2, as compared with the conventional control devices 200,each of the control devices 400 is equipped with an output switch 402,an input switch 403, a synchronous signal comparison circuit 405, and amode changeover switch 401.

[0107] The detection signal of the rotation detecting sensor 124A isinput to the output switch 402, which can output it as the rotationsynchronization signal 501. Further, the output switch 402 is controlledby the master/slave signal 502, switching between the output andnon-output of the rotation synchronization signal 501.

[0108] The rotation synchronization signal 501 is input to the inputswitch 403, which can output it to the synchronous signal comparisoncircuit 405 as a predetermined signal (hereinafter referred to as thecomparison signal). Further, like the output switch 402, the inputswitch 403 is controlled by the master/slave signal 502, switchingbetween taking-in and non-taking-in of the rotation synchronizationsignal 501.

[0109] Further, input to the synchronous signal comparison circuit 405is the detection signal of the rotation detecting sensor 124A. And, thissynchronous signal comparison circuit 405 contains a phase locked loopcircuit (hereinafter referred to as the PLL circuit) serving as a phasecontrol circuit, etc., and performs, for example, phase comparisonbetween the detection signal of the rotation detecting sensor 124A and acomparison signal which is the output of the input switch 403,outputting the comparison result to the mode changeover switch 401.

[0110] The mode changeover switch 401 can effect switching between theoutput of the synchronous signal comparison circuit 405 (hereinafterreferred to as the synchronous mode side) and the output of thecomparator 242 (hereinafter referred to as the asynchronous mode side).Further, the mode changeover switch 401 is also controlled by themaster/slave signal 502, supplying the switched output to the gatesignal generating circuit 246.

[0111] In this construction, during synchronous operation, the outputswitch 402, the input switch 403, and the mode changeover switch 401 arecontrolled as follows by the master/slave signal 502, respectively.

[0112] The switch changeover by the master/slave signal 502 will bedescribed with reference to FIG. 3. In describing this embodiment, thecontrol device 400A will be regarded as the master device, and thecontrol devices 400B, 400C, and 400D will be regarded as the slavedevices. In this case, the master/slave signal 502 sets the controldevice 400A as the master device, and sets the control devices 400B,400C, and 400D as the slave devices.

[0113] In FIG. 3, in the control device 400A serving as the master (themaster sections in the drawing), the output switch 402 thereof is placedin a state of “outputting a rotation synchronization signal”, the inputswitch 403 is placed in a state of “not taking in the rotationsynchronization signal”, and the mode changeover switch 401 is placed inthe “asynchronous mode side”.

[0114] Thus, from the control device 400A serving as the master, therotation synchronization signal 501 is output through the output switch402 thereof.

[0115] Further, in the control device 400A, the mode changeover switch401 has been switched to the asynchronous mode side, so that the outputof the comparator 242 is transmitted to the gate signal generatingcircuit 246. Thus, the rotation control on the rotor shaft 113 in thecontrol device 400A serving as the master is conducted in the samemanner as in the prior art.

[0116] In each of the control devices 400B, 400C, and 400D serving asslaves (the slave sections in the drawing), the output switch 402 isplaced in the state of “not outputting the rotation synchronizationsignal”, the input switch 403 is placed in the state of “taking in therotation synchronization signal”, and the mode changeover switch 401 isplaced on the “synchronous mode side”.

[0117] That is, in each of the control devices 400B, 400C, and 400Dserving as slaves, the rotation synchronization signal 501 is taken inthrough the input switch 403, and a comparison signal corresponding tothe rotation synchronization signal 501 is output to the synchronoussignal comparison circuit 405.

[0118] And, in the synchronous signal comparison circuit 405, the phaseof each signal is detected from the rise/fall of the detection signal ofthe rotation detecting sensor 124A and the rise/fall of the comparisonsignal. Further, in the synchronous signal comparison circuit 405,matching and mismatching of phase is judged with respect to the phase ofeach signal.

[0119] And, since the mode changeover switch 401 is placed on thesynchronous mode side, the comparison result obtained by the synchronoussignal comparison circuit 405 is transmitted to the gate signalgenerating circuit 246. In the gate signal generating circuit 246, therotating speed of the rotor shaft 113 is increased or reduced based onthe comparison result obtained by the synchronous signal comparisoncircuit 405 to effect phase matching process between detection signal ofthe rotation detecting sensor 124A and the rotation synchronizationsignal 501. FIG. 4 shows how this phase matching process is performed inthe slave device.

[0120] As shown in FIG. 4, in case 1, the phase of the detection signalof the rotation detecting sensor 124A is behind the phase of therotation synchronization signal 501. Thus, the synchronous signalcomparison circuit 405 performs control on the gate signal generatingcircuit 246 so as to increase the rotating speed of the rotor shaft 113.

[0121] In case 2, the phase of the detection signal of the rotationdetecting sensor 124A is ahead of the phase of the rotationsynchronization signal 501. Thus, the synchronous signal comparisoncircuit 405 performs control on the gate signal generating circuit 246so as to reduce the rotating speed of the rotor shaft 113.

[0122] As in the prior art, the gate signal generating circuit 246,which has undergone such control, controls the gate signal of each ofthe transistors 226, 228, 230, 232, 234, and 236 of the motor drivingcircuit 222 to vary the rotating speed of the rotor shaft 113.

[0123] And, in case 3, the phase of the rotation synchronization signal501 and the phase of the detection signal of the rotation detectingsensor 124A are matched with each other.

[0124] As a result, the RPM and phases of the respective rotor shafts113 of the turbo-molecular pumps 100A, 100B, 100C, and 100D are matchedwith each other.

[0125] Thus, the turbo-molecular pumps 100A, 100B, 100C, and 100Dinvolve no beat or low-frequency vibration.

[0126] Thus, even when a plurality of turbo-molecular pumps 100 arearranged, it is possible to realize a pump system in which no beat orlow-frequency vibration is generated by matching the RPM and phases ofthe respective rotor shafts 113 of the turbo-molecular pumps 100 witheach other.

[0127] It is not necessary for both the RPM and phases of the rotorshafts 113 to be matched with each other. A beat can be sufficientlyprevented by matching the RPM alone.

[0128] While in this embodiment the control device 400A serves as themaster, the control is the same if one of the other control devices400B, 400C, and 400D serves as the master.

[0129] The way in which the master device is selected from the pluralityof control devices 400 may be previously determined by the pump systemoperator or the like, or determined through automatic setting in thesynchronous operation controller 500.

[0130] In the case of automatic setting, selection may be effected basedon the uptime, the volume, failure records, etc. of each turbo-molecularpump 100. In this way, it is possible to select the turbo-molecular pump100, which is resistant to failure, as the master.

[0131] Further, while in this embodiment an example of providing fourturbo-molecular pumps 100 and four control devices 400 has beenexplained, this should not be construed restrictively. It is alsopossible to provide two or three, or five or more turbo-molecular pumpsand control devices, respectively.

[0132] Further, while in this embodiment communication by the rotationsynchronization signal 501 is effected between the control devices 400A,400B, 400C, and 400D through a wired system, this should not beconstrued restrictively. It is also possible to establish communicationthrough a wireless system.

[0133] Further, similarly, it is possible to establish communicationusing the master/slave signal 502 between the control devices 400 andthe synchronous operation controller 500 through a wireless system.

[0134] Thus, taking into account the condition of the place where thecontrol devices 400, etc. are arranged, a system can be selected inwhich the rotation synchronization signal 501 can be easily transmitted.

[0135] Further, while in this embodiment the master/slave signal 502 isinput to each control device 400, and the rotation synchronizationsignal 501 is transmitted between the control devices 400, this shouldnot be construed restrictively. It is also possible to adopt anarrangement in which the master/slave signal 502 is input to eachturbo-molecular pump 100 or an arrangement in which the rotationsynchronization signal 501 is transmitted between the turbo-molecularpumps 100.

[0136] Next, a second embodiment of the present invention will bedescribed.

[0137] While in the pump system of the first embodiment, communicationbetween the synchronous operation controller and the control devices iseffected by the master/slave signal, in the pump system of the secondembodiment, communication is effected further using an operation/stopsignal and an alarm signal.

[0138]FIG. 5 is a schematic structural diagram showing a pump systemaccording to the second embodiment of the present invention. Thecomponents which are the same as those of FIG. 1 are indicated with thesame reference numerals, and a description of such components will beomitted.

[0139] Each of the control devices 400A, 400B, 400C, and 400D outputs analarm signal 503 to the synchronous operation controller 500. The alarmsignal 503 is a signal informing of any failure in the turbo-molecularpumps 100 and the control devices 400 and indicating the maintenancetime for them.

[0140] Further, the synchronous operation controller 500 outputs anoperation/stop signal 504 to each of the control devices 400A, 400B,400C, and 400D. This operation/stop signal 504 is a signal for operatingor stopping the turbo-molecular pumps 100 and the control devices 400.

[0141] As in the first embodiment, in this arrangement, the RPM andphases of the rotor shafts 113 of the turbo-molecular pumps 100A, 100B,100C, and 100D are controlled so as to be matched with each other.

[0142] During this synchronous operation, when the alarm signal 503 isoutput from one of the control devices 400A, 400B, 400C, and 400D due tofailure or the like, the synchronous operation controller 500 outputsthrough its own control the operation/stop signal 504 to that controldevice 400 out of order, bringing the control device 400 and theturbo-molecular pump 100 to a stop so that the control device 400 out oforder may not adversely affect the other control devices 400.

[0143] And, when the control device 400 brought to a stop because offailure or the like is a slave device, the other control devices 400performing synchronous operation are not affected since a slave deviceonly takes in the rotation synchronization signal 501. Thus, synchronousoperation is continued with the remaining normal control devices alone.

[0144] When the control device 400 brought to a stop because of failureor the like is the master device, there is a fear that the other slavedevices will become unable to operate since the rotation synchronizationsignal 501 is not output from the master device.

[0145] In this embodiment, however, the synchronous operation controller500 controls the operation/stop of the control devices 400 and, as inthe first embodiment, also outputs the master/slave signal 502, so thatit is possible to make a judgment as to whether the control device 400at rest is the master or not.

[0146] Thus, when the master device has stopped operating, thesynchronous operation controller 500 causes the slave devices to stopsynchronous operation to enable all the slave devices to operateindividually.

[0147] In this case, the output switch 402, the input switch 403, andthe mode changeover switch 401 in each slave device are switched by themaster/slave signal 502 as shown in FIG. 3.

[0148] That is, in every one of the control devices 400 operatingindividually (the individual operation section in the drawing), theoutput switch 402 is placed in the state of “not outputting the rotationsynchronization signal”, the input switch 403 is placed in the state of“not taking in rotation synchronization signal”, and the mode changeoverswitch 401 is placed on the “asynchronous mode side”.

[0149] Thus, as in the prior art, these control devices 400 control ontheir own the RPM, etc. of the rotor shafts 113 of the turbo-molecularpumps 100.

[0150] Thus, even in the event of failure or the like in the masterdevice during synchronous operation, it is possible to continueoperation without stopping the slave devices.

[0151] While in this embodiment the synchronous operation controller 500outputs, through its own control, the operation/stop signal 504 to thefailed maser control device 400 to bring it to a stop, causing all theremaining slave control devices 400 to operate individually, this shouldnot be construed restrictively.

[0152] For example, when the alarm signal 503 is output from the controldevice 400 suffering failure or the like, the maintenance operator orthe like for the pump system may depress, for example, a stop button(not shown) of the master control device 400 to stop that control device400, causing all the remaining slave devices to operate individually.

[0153] Further, as in the first embodiment, the alarm signal 503 and theoperation/stop signal 504 may be transmitted through a wireless system.

[0154] Next, a third embodiment of the present invention will bedescribed.

[0155] While the pump system of the second embodiment is controlled suchthat if the master device suffers failure or the like during synchronousoperation, the slave devices operate individually, the pump system ofthe third embodiment is controlled such that even if the master devicesuffers failure or the like, synchronous operation is performed with theremaining slave devices alone.

[0156] The construction of the pump system of this embodiment is thesame as that of the second embodiment (FIG. 5).

[0157] As in the second embodiment, in this construction, when, duringsynchronous operation, the alarm signal 503 is output due to failure orthe like from one of the control devices 400A, 400B, 400C, and 400D, thesynchronous operation controller 500 brings the control device 400 andthe turbo-molecular pump 100 that are out of order to a stop.

[0158] And, as in the second embodiment, when the control device 400brought to a stop due to failure or the like is the master device, thereis a fear of the other slave devices becoming incapable of operation.

[0159] In this embodiment, however, when the master device comes to ahalt, one of the slave devices is newly switched to the master device,by means of which control is performed so as to start synchronousoperation again.

[0160]FIG. 6 shows how this slave/master switching is effected on thecontrol device.

[0161] In FIG. 6, as stated above, during normal operation, the controldevice 400A serves as the master device, and the control devices 400B,400C, and 400D serve as the slave devices.

[0162] Suppose the control device 400A, serving as the master device,has come to a halt due to failure or the like. In this case, one of thecontrol devices 400B, 400C, and 400D serving as the slave devices andnot out of order is switched to the master device according to apredetermined order. In this embodiment, it is assumed that the settingof the switching order is previously made as follows by the maintenanceoperator or the like for the pump system: (1) control device 400B, (2)control device 400C, and (3) control device 400D.

[0163] Thus, control is effected such that the control device 400B isswitched to the master device. That is, the output switch 402, the inputswitch 403, and the mode changeover switch 401 of the control device400B are switched from the “slave” state to the “master” state in FIG. 3by the master/slave signal 502.

[0164] And, these three control devices 400B, 400C, and 400D startsynchronous operation again through the same control as in the firstembodiment.

[0165] Suppose, further, that the control device 400B, which has newlybecome the master device, has come to a halt during this operation.

[0166] In this case also, control is effected such that the controldevice 400C becomes the master device according to the above-mentionedpredetermined order.

[0167] And, the control devices 400C and 400D start synchronousoperation again.

[0168] Suppose, further, that the control device 400C has come to a haltduring this operation.

[0169] In this case, it is the control device 400D alone that is inoperation, so that, in order to continue operation, the control device400D is controlled so as to stop synchronous operation and to operateindividually. The output switch 402, the input switch 403, and the modechangeover switch 401 of the control device 400D are switched from the“slave” state to the “individual operation” state in FIG. 3 by themaster/slave signal 502.

[0170] And, with the control device 400D alone, the RPM, etc. of therotor shafts 113 are controlled in the same manner as in the prior art.

[0171] In this way, even if the master device suffers failure or thelike during synchronous operation, it is possible to continuesynchronous operation using the slave devices only, without stopping theslave devices.

[0172] In order that the operation of the control device 400 which is tobecome the master device may not be adversely affected, it is desirablethat the master device suffering failure or the like be separated fromthe slave devices.

[0173] In view of this, when the master device suffering failure or thelike is brought to a stop, switching is effected, for example, to the“individual operation” state shown in FIG. 3.

[0174] While in the above description of the embodiment the slavedevices are switched according to an order previously determined by theoperator or the like, this should not be construed restrictively.

[0175] In order that the turbo-molecular pump 100 which is relativelyfree from failure may become the master, it is possible to determine theswitching order based on the uptime of each turbo-molecular pump 100,the volume, failure history, etc. of the turbo-molecular pump. Thismakes it possible to switch the turbo-molecular pump 100 which isrelatively free from failure to the master.

[0176] Next, a fourth embodiment of the present invention will bedescribed.

[0177] While in the first embodiment the entire pump system is caused toperform synchronous operation by the rotation synchronization signaloutput from the master device, in the fourth embodiment, the entire pumpsystem is caused to perform synchronous operation by a rotationsynchronization signal output from the synchronous operation controller.

[0178]FIG. 7 is a schematic structural diagram showing a pump systemaccording to the fourth embodiment. The components which are the same asthose of FIG. 1 are indicated with the same reference numerals, and adescription of such components will be omitted.

[0179] In FIG. 7, a rotation synchronization signal 505 generated by thesynchronous operation controller 500 is input to each of the controldevices 400A, 400B, 400C, and 400D.

[0180] The rotation synchronization signal 505 is generated in theinterior (not shown) of the synchronous operation controller 500, usinga crystal oscillator similar to that of the reference value settingcircuit 244 of the first embodiment.

[0181] In this construction, in the control devices 400A, 400B, 400C,and 400D, the RPM and phases of the rotor shafts 113 of theturbo-molecular pumps 100A, 100B, 100C, and 100D are simultaneouslycontrolled based on the same input rotation synchronization signal 505.

[0182] At this time, the RPM and phases of the rotors 113 are controlledbased on the crystal oscillator in the synchronous operation controller500, so that the accuracy in the synchronous control can be furtherenhanced.

[0183] Thus, no beat or low-frequency vibration is generated.

[0184] As a result, it is possible to obtain the same effect as that ofthe first embodiment of the present invention.

[0185] While in this embodiment described above the rotationsynchronization signal 505 is generated in the synchronous operationcontroller 500, this should not be construed restrictively. It may begenerated separately from the synchronous operation controller 500.

[0186] As described above, in accordance with the present invention, therotating conditions of the rotary members of the slave vacuum pumps aremade to be in synchronism with the rotating condition of the rotarymember of the master vacuum pump, so that even when a plurality ofvacuum pumps are arranged, it is possible to prevent a beat andlow-frequency vibration by matching the RPM and phases of the rotarymembers of the vacuum pumps with each other.

[0187] Further, the rotating condition of the rotary member iscontrolled based on comparison with a reference RPM and/or rotationphase set for each slave vacuum pump, so that even if the master controldevice comes to a halt, it is possible to continue operation withoutstopping the slave control device.

[0188] And, there is provided a re-setting means for effectingre-setting using one of the slave control devices as the master controldevice, so that even if the master control device comes to a halt, it ispossible to perform operation with the RPM and phases of the rotarymembers of the vacuum pumps being matched with each other.

[0189] Further, the rotating condition of the rotary member of eachvacuum pump is made to be in synchronism with the synchronous signaloutput from the synchronous signal generating means, so that even when aplurality of vacuum pumps are arranged, it is possible to prevent a beatand low-frequency vibration by matching the RPM and phases of the rotarymembers of the vacuum pumps.

What is claimed is:
 1. A vacuum pump system equipped with N vacuum pumpseach of which is equipped with a rotary member and a motor for rotatingthe rotary member and which are mounted side by side to equipment fromwhich a predetermined gas is to be sucked, and control devices connectedto the vacuum pumps and adapted to control at least one of RPM androtation phases representing rotating conditions of the rotary members,the vacuum pump system comprising: setting means for setting one of thecontrol devices as a master control device and (N−1) control devicesexcluding the master control device as slave control devices; masterdetection means for detecting the rotating condition of the rotarymember of a master vacuum pump of the vacuum pumps to which the mastercontrol device is connected; slave detection means for detecting therotating conditions of the rotary members of slave vacuum pumps of thevacuum pumps to which the slave control devices are connected; andcontrol means for controlling such that the rotating conditions of therotary members detected by the slave detection means are in synchronismwith the rotating condition of the rotary member detected by the masterdetection means.
 2. A vacuum pump system according to claim 1, whereinthe control means includes: a motor driving circuit for supplying powerto the motor; a gate signal generating circuit for controlling the poweroutput from the motor driving circuit; and a synchronous signalcomparison circuit for comparing the rotating condition of the rotarymember detected by the master detection means with the rotatingconditions of the rotary members detected by the slave detection means,and outputting the comparison result to the gate signal generatingcircuit.
 3. A vacuum pump system according to claim 2, wherein thesetting means outputs a master/slave signal making it possible to setthe control devices after switching the control devices to master orslave side.
 4. A vacuum pump system according to claim 3, wherein theswitching to master or slave side by the master/slave signal is effectedin an order previously set in the setting means.
 5. A vacuum pump systemaccording to claim 4, wherein the master/slave signal is transmittedthrough a wired or wireless system.
 6. A vacuum pump system according toclaim 3, wherein the switching to master or slave side by themaster/slave signal is effected automatically in the setting means.
 7. Avacuum pump system according to claim 6, wherein the automatic switchingin the setting means is based on at least one of an uptime of the vacuumpumps, a volume of the vacuum pumps, and a failure history of the vacuumpumps.
 8. A vacuum pump system according to claim 7, wherein themaster/slave signal is transmitted through a wired or wireless system.9. A vacuum pump system according to claim 1, further comprisingstopping means for stopping the vacuum pumps, wherein when the mastervacuum pump is stopped by the stopping means, the control means controlsthe rotating conditions of the rotary members detected by the slavedetection means based on comparison with at least one of a reference RPMand rotation phase set for the slave vacuum pumps.
 10. A vacuum pumpsystem according to claim 9, wherein when any of the slave vacuum pumpsis stopped by the stopping means, the control means controls therotating conditions of the rotary members of the slave vacuum pumpsother than the stopped one based on comparison with the rotatingcondition of the rotary member detected by the master detection means.11. A vacuum pump system according to claim 10, wherein the stoppingmeans is input with an alarm signal indicating at least one of failureand maintenance time of the control devices and the vacuum pumps andoutputs an operation/stop signal making it possible to switch betweenthe operation and stopping of the vacuum pumps, and wherein when thealarm signal is output from at least one of the control devices and thevacuum pumps, the operation/stop signal output for the vacuum pumps isswitched to the stop side.
 12. A vacuum pump system according to claim11, wherein at least one of the alarm signal and the operation/stopsignal is transmitted through a wired or wireless system.
 13. A vacuumpump system according to claim 9, further comprising failure detectingmeans for detecting failure in the control devices and the vacuum pumps,wherein the stopping means stops any of the vacuum pumps in whichfailure is detected by the failure detecting means.
 14. A vacuum pumpsystem according to claim 13, wherein the failure detecting meansoutputs the alarm signal.
 15. A vacuum pump system according to claim 1,further comprising: stopping means for stopping the vacuum pumps; andre-setting means for, when the master vacuum pump is stopped by thestopping means, re-setting one of the slave control devices as themaster control device.
 16. A vacuum pump system according to claim 15,further comprising failure detecting means for detecting failure in thecontrol devices and the vacuum pumps, wherein the stopping means stopsany of the vacuum pumps in which failure is detected by the failuredetecting means.
 17. A vacuum pump system according to claim 16, whereinthe failure detecting means outputs the alarm signal.
 18. A vacuum pumpsystem according to claim 15, wherein the re-setting by the re-settingmeans is effected based on a predetermined order.
 19. A vacuum pumpsystem according to claim 18, wherein the order is determined based onat least one of an uptime of the vacuum pumps, a volume of the vacuumpumps, and a failure history of the vacuum pumps.
 20. A vacuum pumpsystem according to claim 19, wherein the stopping means is input withan alarm signal indicating at least one of failure and maintenance timeof the control devices and the vacuum pumps and outputs anoperation/stop signal making it possible to switch between the operationand stopping of the vacuum pumps, and wherein when the alarm signal isoutput from at least one of the control devices and the vacuum pumps,the operation/stop signal output for the vacuum pumps is switched to thestop side.
 21. A vacuum pump system according to claim 20, wherein there-setting means is input with the alarm signal indicating at least oneof failure and maintenance time of the control devices and the vacuumpumps and outputs the master/slave signal, and wherein, when the alarmsignal is output from at least one of the master control device and themaster vacuum pump, the master/slave signal output for one of the slavecontrol devices is switched to the master side.
 22. A vacuum pump systemaccording to claim 21, wherein, when the alarm signal is output from atleast one of the master control device and the master vacuum pump, there-setting means switches the master/slave signal output for the mastercontrol device to the slave side.
 23. A vacuum pump system according toclaim 22, wherein at least one of the alarm signal and theoperation/stop signal is transmitted through a wired or wireless system.24. A vacuum pump system according to claim 18, further comprisingfailure detecting means for detecting failure in the control devices andthe vacuum pumps, wherein the stopping means stops any of the vacuumpumps in which failure is detected by the failure detecting means.
 25. Avacuum pump system according to claim 24, wherein the failure detectingmeans outputs the alarm signal.
 26. A vacuum pump system according toclaim 15, wherein when the master vacuum pump is stopped by the stoppingmeans and all the slave vacuum pumps but one are stopped, the controlmeans controls the rotating condition of the rotary member of the oneslave vacuum pump based on comparison with at least one of a referenceRPM and rotation phase set for the slave vacuum pumps.
 27. A vacuum pumpsystem according to claim 26, wherein the re-setting by the re-settingmeans is effected based on a predetermined order.
 28. A vacuum pumpsystem according to claim 27, wherein the order is determined based onat least one of an uptime of the vacuum pumps, a volume of the vacuumpumps, and a failure history of the vacuum pumps.
 29. A vacuum pumpsystem according to claim 28, wherein the stopping means is input withan alarm signal indicating at least one of failure and maintenance timeof the control devices and the vacuum pumps and outputs anoperation/stop signal making it possible to switch between the operationand stopping of the vacuum pumps, and wherein when the alarm signal isoutput from at least one of the control devices and the vacuum pumps,the operation/stop signal output for the vacuum pumps is switched to thestop side.
 30. A vacuum pump system according to claim 29, wherein there-setting means is input with the alarm signal indicating at least oneof failure and maintenance time of the control devices and the vacuumpumps and outputs the master/slave signal, and wherein, when the alarmsignal is output from at least one of the master control device and themaster vacuum pump, the master/slave signal output for one of the slavecontrol devices is switched to the master side.
 31. A vacuum pump systemaccording to claim 30, wherein, when the alarm signal is output from atleast one of the master control device and the master vacuum pump, there-setting means switches the master/slave signal output for the mastercontrol device to the slave side.
 32. A vacuum pump system according toclaim 31, wherein at least one of the alarm signal and theoperation/stop signal is transmitted through a wired or wireless system.33. A vacuum pump system according to claim 26, further comprisingfailure detecting means for detecting failure in the control devices andthe vacuum pumps, wherein the stopping means stops any of the vacuumpumps in which failure is detected by the failure detecting means.
 34. Avacuum pump system according to claim 33, wherein the failure detectingmeans outputs the alarm signal.
 35. A vacuum pump system according toclaim 27, further comprising failure detecting means for detectingfailure in the control devices and the vacuum pumps, wherein thestopping means stops any of the vacuum pumps in which failure isdetected by the failure detecting means.
 36. A vacuum pump systemaccording to claim 35, wherein the failure detecting means outputs thealarm signal.
 37. A vacuum pump system equipped with N vacuum pumps eachof which is equipped with a rotary member and a motor for rotating therotary member and which are mounted side by side to equipment from whicha predetermined gas is to be sucked, and control devices connected tothe vacuum pumps and adapted to control at least one of RPM and rotationphases representing rotating conditions of the rotary members, thevacuum pump system comprising: synchronous signal generating means forgenerating and outputting a predetermined synchronous signal; detectingmeans for detecting the rotating conditions of the rotary members of thevacuum pumps; and control means for controlling such that the rotatingconditions of the rotary members detected by the detecting means are insynchronism with the synchronous signal output from the synchronoussignal generating means.
 38. A vacuum pump system according to claim 37,wherein the synchronous signal is at least one of a reference RPM androtation phase set to be only one for the N vacuum pumps.
 39. A vacuumpump system according to claim 38, wherein the control means includes: amotor driving circuit for supplying power to the motor; a gate signalgenerating circuit for controlling the power output from the motordriving circuit; and a synchronous signal comparison circuit forcomparing the synchronous signal output from the synchronous signalgenerating means with the rotating conditions of the rotary membersdetected by the detecting means and outputting the comparison result tothe gate signal generating circuit.
 40. A vacuum pump system accordingto claim 39, wherein the synchronous signal generating means is acrystal oscillator.
 41. A vacuum pump system according to claim 40,wherein the synchronous signal is transmitted through a wired orwireless system.
 42. A vacuum pump system comprising: a rotary member; amotor for rotating the rotary member; detecting means for detecting atleast one of RPM and rotation phase representing rotating condition ofthe rotary member; internal comparison means for comparing the rotatingcondition of the rotary member detected by the detecting means with atleast one of a reference RPM and rotation phase; external comparisonmeans for comparing the rotating condition of the rotary member detectedby the detecting means with an external synchronous signal; switchingmeans for selecting the transmission of the synchronous signal to theexterior or the reception of the synchronous signal from the exteriorbased on a predetermined switching signal, and which is input with thecomparison result of the internal comparison means and the comparisonresult of the external comparison means, and outputs an output signalwhich is selected from one of the input comparison results based on theswitching signal; and rotation control means for controlling therotating condition of the rotary member based on the output signaloutput from the switching means.
 43. A vacuum pump system according toclaim 42, wherein the switching means includes: an output switch thatselects between transmission and non-transmission of the synchronoussignal to the exterior based on the switching signal; an input switchthat selects between reception and non-reception of the synchronoussignal from the exterior based on the switching signal; and a modechangeover switch which is input with the comparison result of theinternal comparison means and the comparison result of the externalcomparison means, and outputs an output signal which is selected fromone of the input comparison results based on the switching signal.
 44. Avacuum pump system according to claim 42, which is equipped with Nvacuum pump devices each of which is composed of the rotary member, themotor, the detecting means, the internal comparison means, the externalcomparison means, the switching means, and the rotation control means,wherein the switching signal is a signal which sets one of the vacuumpump devices as a master device and sets (N−1) vacuum pump devicesexcluding the master device as slave devices; wherein, when the masterdevice is set by the switching signal, the switching means selects thecomparison result of the internal comparison means while transmittingthe rotating condition of the rotary member detected by the detectingmeans to the exterior as the synchronous signal; and wherein, when theslave devices are set by the switching signal, the switching meansselects the comparison result of the external comparison means whilereceiving the synchronous signal from the exterior.
 45. A vacuum pumpsystem according to claim 44, wherein the synchronous signal istransmitted through a wired or wireless system.
 46. A vacuum pump systemaccording to claim 44, wherein the rotation control means includes: amotor driving circuit that supplies power to the motor; and a gatesignal generating circuit that controls the power output from the motordriving circuit based on the output signal output from the switchingmeans.
 47. A vacuum pump system according to claim 46, furthercomprising setting means for outputting the switching signal, whereinthe switching to master or slave side by the switching signal iseffected in an order previously set in the setting means.
 48. A vacuumpump system according to claim 47, wherein the synchronous signal istransmitted through a wired or wireless system.
 49. A vacuum pump systemaccording to claim 46, further comprising setting means for outputtingthe switching signal, wherein the switching to master or slave side bythe switching signal is effected automatically in the setting means. 50.A vacuum pump system according to claim 49, wherein the automaticswitching in the setting means is based on at least one of an uptime ofthe vacuum pump devices, a volume of the vacuum pump devices, and afailure history of the vacuum pump devices.
 51. A vacuum pump systemaccording to claim 50, wherein the synchronous signal is transmittedthrough a wired or wireless system.
 52. A vacuum pump system accordingto claim 44, further comprising stopping means for stopping the vacuumpump devices, wherein, when the master device is stopped by the stoppingmeans, the switching means of the slave devices selects the comparisonresult of the internal comparison means.
 53. A vacuum pump systemaccording to claim 52, wherein, when any of the slave devices is stoppedby the stopping means, the switching means of the slave devices otherthan the stopped one selects the comparison result of the externalcomparison means while receiving the synchronous signal from theexterior.
 54. A vacuum pump system according to claim 53, wherein thestopping means is input with an alarm signal indicating at least one offailure and maintenance time of the vacuum pump devices and outputs anoperation/stop signal making it possible to switch between the operationand stopping of the vacuum pump devices, and wherein when the alarmsignal is output from any of the vacuum pump devices, the operation/stopsignal output for the vacuum pump devices is switched to the stop side.55. A vacuum pump system according to claim 54, wherein at least one ofthe alarm signal and the operation/stop signal is transmitted through awired or wireless system.
 56. A vacuum pump system according to claim52, further comprising failure detecting means for detecting failure inthe vacuum pump devices, wherein the stopping means stops any of thevacuum pump devices in which failure is detected by the failuredetecting means.
 57. A vacuum pump system according to claim 56, whereinthe failure detecting means outputs the alarm signal.
 58. A vacuum pumpsystem according to claim 44, further comprising: stopping means forstopping the vacuum pump devices; and re-setting means for, when themaster device is stopped by the stopping means, re-setting one of theslave devices as the master device.
 59. A vacuum pump system accordingto claim 58, further comprising failure detecting means for detectingfailure in the vacuum pump devices, wherein the stopping means stops anyof the vacuum pump devices in which failure is detected by the failuredetecting means.
 60. A vacuum pump system according to claim 59, whereinthe failure detecting means outputs the alarm signal.
 61. A vacuum pumpsystem according to claim 58, wherein the re-setting by the re-settingmeans is effected based on a predetermined order.
 62. A vacuum pumpsystem according to claim 61, wherein the order is determined based onat least one of an uptime of the vacuum pump devices, a volume of vacuumpump devices, and a failure history of the vacuum pump devices.
 63. Avacuum pump system according to claim 62, wherein the stopping means isinput with an alarm signal indicating at least one of failure andmaintenance time of the vacuum pump devices and outputs anoperation/stop signal making it possible to switch between the operationand stopping of the vacuum pump devices, and wherein when the alarmsignal is output from any of the vacuum pump devices, the operation/stopsignal output for the vacuum pump devices is switched to the stop side.64. A vacuum pump system according to claim 63, wherein the re-settingmeans is input with the alarm signal indicating at least one of failureand maintenance time of the vacuum pump devices and outputs theswitching signal, and wherein, when the alarm signal is output from themaster device, the switching signal output for one of the slave devicesis switched to the master side.
 65. A vacuum pump system according toclaim 64, wherein, when the alarm signal is output from the masterdevice, the re-setting means switches the switching signal output forthe master device to the slave side.
 66. A vacuum pump system accordingto claim 65, wherein at least one of the alarm signal and theoperation/stop signal is transmitted through a wired or wireless system.67. A vacuum pump system according to claim 66, further comprisingfailure detecting means for detecting failure in the vacuum pumpdevices, wherein the stopping means stops any of the vacuum pump devicesin which failure is detected by the failure detecting means.
 68. Avacuum pump system according to claim 67, wherein the failure detectingmeans outputs the alarm signal.
 69. A vacuum pump system according toclaim 58, wherein, when the master device is stopped by the stoppingmeans and all the slave devices but one are stopped, the switching meansof the slave device selects the comparison result of the internalcomparison means.
 70. A vacuum pump system according to claim 69,wherein the re-setting by the re-setting means is effected based on apredetermined order.
 71. A vacuum pump system according to claim 70,wherein the order is determined based on at least one of an uptime ofthe vacuum pump devices, a volume of vacuum pump devices, and a failurehistory of the vacuum pump devices.
 72. A vacuum pump system accordingto claim 71, wherein the stopping means is input with an alarm signalindicating at least one of failure and maintenance time of the vacuumpump devices and outputs an operation/stop signal making it possible toswitch between the operation and stopping of the vacuum pump devices,and wherein when the alarm signal is output from any of the vacuum pumpdevices, the operation/stop signal output for the vacuum pump devices isswitched to the stop side.
 73. A vacuum pump system according to claim72, wherein the re-setting means is input with the alarm signalindicating at least one of failure and maintenance time of the vacuumpump devices and outputs the switching signal, and wherein, when thealarm signal is output from the master device, the switching signaloutput for one of the slave devices is switched to the master side. 74.A vacuum pump system according to claim 73, wherein, when the alarmsignal is output from the master device, the re-setting means switchesthe switching signal output for the master device to the slave side. 75.A vacuum pump system according to claim 74, wherein at least one of thealarm signal and the operation/stop signal is transmitted through awired or wireless system.
 76. A vacuum pump system according to claim69, further comprising failure detecting means for detecting failure inthe vacuum pump devices, wherein the stopping means stops any of thevacuum pump devices in which failure is detected by the failuredetecting means.
 77. A vacuum pump system according to claim 76, whereinthe failure detecting means outputs the alarm signal.
 78. A vacuum pumpsystem according to claim 70, further comprising failure detecting meansfor detecting failure in the vacuum pump devices, wherein the stoppingmeans stops any of the vacuum pump devices in which failure is detectedby the failure detecting means.
 79. A vacuum pump system according toclaim 78, wherein the failure detecting means outputs the alarm signal.80. A vacuum pump system according to claim 42, which is equipped withsynchronous signal generating means for generating and outputting thesynchronous signal, and N vacuum pump devices each of which is composedof the rotary member, the motor, the detecting means, the internalcomparison means, the external comparison means, the switching means,and the rotation control means, wherein the switching means selects thecomparison result of the external comparison means while receiving thesynchronous signal from the exterior.
 81. A vacuum pump system accordingto claim 80, wherein the synchronous signal is at least one of areference RPM and rotation phase set to be only one for the N vacuumpump devices.
 82. A vacuum pump system according to claim 81, whereinthe rotation control means includes: a motor driving circuit thatsupplies power to the motor; and a gate signal generating circuit thatcontrols the power output from the motor driving circuit based on theoutput signal output from the switching means.
 83. A vacuum pump systemaccording to claim 82, wherein the synchronous signal generating meansis a crystal oscillator.
 84. A vacuum pump system according to claim 83,wherein the synchronous signal is transmitted through a wired orwireless system.
 85. A vacuum pump system according to claim 1, whereineach of the rotary members has rotary blades and a rotor shaft arrangedat the center of the rotary blades, and is equipped with magneticbearing means which magnetically levitates the rotor shaft forpositional adjustment in at least one of the radial direction and theaxial direction.
 86. A vacuum pump system according to claim 37, whereineach of the rotary members has rotary blades and a rotor shaft arrangedat the center of the rotary blades, and is equipped with magneticbearing means which magnetically levitates the rotor shaft forpositional adjustment in at least one of the radial direction and theaxial direction.
 87. A vacuum pump system according to claim 42, whereineach of the rotary members has rotary blades and a rotor shaft arrangedat the center of the rotary blades, and is equipped with magneticbearing means which magnetically levitates the rotor shaft forpositional adjustment in at least one of the radial direction and theaxial direction.
 88. A vacuum pump RPM control method for a vacuum pumpsystem equipped with N vacuum pumps each of which is equipped with arotary member and a motor for rotating the rotary member and which aremounted side by side to equipment from which a predetermined gas is tobe sucked, and control devices connected to the vacuum pumps and adaptedto control the RPM of the rotary members, wherein the RPM of the rotarymembers are all controlled to be the same.
 89. A vacuum pump RPM controlmethod according to claim 88, wherein each of the rotary members hasrotary blades and a rotor shaft arranged at the center of the rotaryblades, and is equipped with magnetic bearing means which magneticallylevitates the rotor shaft for positional adjustment in at least one ofthe radial direction and the axial direction.